NON-INDIGENOUS BRITISH BIRDS. 321 



Azores, in the Barbadoes, Bahamas, and the Galapagos 

 Islands, and possibly elsewhere in the islands of the 

 Pacific. 



Breeding habits : The habits of the Dusky Shear- 

 water are very imperfectly known, but what few have 

 been observed are very similar to those of the Manx 

 Shearwater. The bird is gregarious during the nesting 

 season, congregating at various islands to breed, and 

 probably pairing for life. It is a strictly nocturnal bird, 

 scarcely ever being seen abroad during daylight (even 

 infested by eyeless parasites), and as a consequence 

 its actions are little observed. It does not appear to 

 make any nest, but to deposit its Qgg in a burrow in the 

 ground or in hollows under rocks. 



Range of egg colouration and measurement : 

 The Dusky Shearwater only lays one Ggg for a sitting. 

 It is rough and chalky in texture, oval in shape, and 

 pure white. Average measurement, Ti inches in length, 

 by 1*4 inch in breadth. Incubation is performed by 

 both sexes, but the duration of the period is unknown. 



Diagnostic characters : The ^gg of the Dusky 

 Shearwater is much smaller than that of the Manx 

 Shearwater, but whether it can be distinguished from 

 those of other allied species, I am not prepared to say. 

 The egrsfs of no birds are so little known as those of the 

 species in the present family. The locality is of some 

 assistance in identifying them, but as the breeding areas 

 of these birds are little known, even this is a doubtful 

 guide. 



